Galaxy Disks

The formation and evolution of galactic disks is particularly important for understanding how galaxies form and evolve, and the cause of the variety in which they appear to us. Ongoing large surveys, made possible by new instrumentation at wavelengths from the ultraviolet (GALEX), via optical (HST and large groundbased telescopes) and infrared (Spitzer) to the radio are providing much new information about disk galaxies over a wide range of redshift. Although progress has been made, the dynamics and structure of stellar disks, including their truncations, are still not well understood. We do now have plausible estimates of disk mass-to-light ratios, and estimates of Toomre's $Q$ parameter show that they are just locally stable. Disks are mostly very flat and sometimes very thin, and have a range in surface brightness from canonical disks with a central surface brightness of about 21.5 $B$-mag arcsec$^{-2}$ down to very low surface brightnesses. It appears that galaxy disks are not maximal, except possibly in the largest systems. Their HI layers display warps whenever HI can be detected beyond the stellar disk, with low-level star formation going on out to large radii. Stellar disks display abundance gradients which flatten at larger radii and sometimes even reverse. The existence of a well-defined baryonic Tully-Fisher relation hints at an approximately uniform baryonic to dark matter ratio. Thick disks are common in disk galaxies and their existence appears unrelated to the presence of a bulge component; they are old, but their formation is not yet understood. Disk formation was already advanced at redshifts of $\sim 2$, but at that epoch disks were not yet quiescent and in full rotational equilibrium. Downsizing is now well-established. The formation and history of star formation in S0s is still not fully understood.Comment: This review has been submitted for Annual Reviews of Astronomy & Astrophysics, vol. 49 (2011); the final printed version will have fewer figures and a somewhat shortened text. A pdf-version of this preprint with high-resolution figures is available from http://www.astro.rug.nl/~vdkruit/jea3/homepage/disks-ph.pdf. (table of contents added; 71 pages, 24 figures, 529 references

Evaluation of selection procedures of an international school

No Abstract. South African Journal of EducationVol. 23(2) 2003: pp. 157-16

Optimization viewpoint on Kalman smoothing, with applications to robust and sparse estimation

In this paper, we present the optimization formulation of the Kalman filtering and smoothing problems, and use this perspective to develop a variety of extensions and applications. We first formulate classic Kalman smoothing as a least squares problem, highlight special structure, and show that the classic filtering and smoothing algorithms are equivalent to a particular algorithm for solving this problem. Once this equivalence is established, we present extensions of Kalman smoothing to systems with nonlinear process and measurement models, systems with linear and nonlinear inequality constraints, systems with outliers in the measurements or sudden changes in the state, and systems where the sparsity of the state sequence must be accounted for. All extensions preserve the computational efficiency of the classic algorithms, and most of the extensions are illustrated with numerical examples, which are part of an open source Kalman smoothing Matlab/Octave package.Comment: 46 pages, 11 figure

Violence as an impediment to a culture of teaching and learning in some South African schools

School violence in South Africa has a long history. Despite the introduction of a new democratic political dispensation in 1994, it appears that violence in schools has not abated. School violence unfortunately impacts negatively on a culture of learning and teaching. In this project, the nature and extent of violence in schools among a sample of learners was investigated. It was found inter alia that school violence has indeed remained a serious problem among these learners and has impacted deleteriously on the culture of teaching and learning in their schools. Two solutions for the eradication of the problem are suggested. South African Journal of Education Vol.24(2) 2004: 170-17

The neural correlates of childhood maltreatment and the ability to understand mental states of others

$\textbf{Background}$: Emotional abuse and emotional neglect are related to impaired interpersonal functioning. One underlying mechanism could be a developmental delay in mentalizing, the ability to understand other people’s thoughts and emotions. $\textbf{Objective}$: This study investigates the neural correlates of mentalizing and the specific relationship with emotional abuse and neglect whilst taking into account the level of sexual abuse, physical abuse and physical neglect. $\textbf{Method}$: The RMET was performed in an fMRI scanner by 46 adolescents (Age: $\textit{M}$ = 18.70, $\textit{SD}$ = 1.46) who reported a large range of emotional abuse and/or emotional neglect. CM was measured using a self-report questionnaire (CTQ). $\textbf{Results}$: Neither severity of emotional abuse nor neglect related to RMET accuracy or reaction time. The severity of sexual abuse was related to an increased activation of the left IFG during mentalization even when controlled for psychopathology and other important covariates. This increased activation was only found in a group reporting both sexual abuse and emotional maltreatment and not when reporting isolated emotional abuse or neglect or no maltreatment. Functional connectivity analysis showed that activation in the left IFG was associated with increased activation in the right insula and right STG, indicating that the IFG activation occurs in a network relevant for mentalizing. $\textbf{Conclusions}$: Being sexually abused in the context of emotional abuse and neglect is related to an increase in activation of the left IFG, which may indicate a delayed development of mirroring other people’s thoughts and emotions. Even though thoughts and emotions were correctly decoded from faces, the heightened activity of the left IFG could be an underlying mechanism for impaired interpersonal functioning when social situations are more complex or more related to maltreatment experiences.This work was supported by The Netherlands Organisation for Scientific Research (NWO)-E.A.C., VICI-grant [453-14- 001], B.M.E., VIDI-grant [016-085-353], A.L.v.H., Rubicon grant [446-13-006] and by the Royal Society-A.L.v.H., Dorothy Hodgkin Fellowship [DH150176]

Play is indispensable for an adequate development of coping with social challenges in the rat

In this study, young rats were deprived of early social interactions during weeks 4 and 5 of life. Different behavior al tests were conducted in adulthood to study the behavioral responses of rats lacking ear ly social experiences. Juvenile deprivation resulted in decreased social activity and an altered sexual pattern, but did not affect locomotor activity or the performance in the elevated plus maze. Furthermore, behavioral and neuroendocrine responses of juvenile isolated rats were dramatically altered when they were confronted with territorial aggression. Juvenile deprived rats did not readily display a submissive posture in response to the resident and showed no immobility behavior after being returned to the resident's territory, while their plasma corticosterone and adrenaline concentrations;were significantly increased compared to nonisolated controls. In contrast, behavioral responses in the shock prod test were not affected by previous isolation. The results suggest that early social experiences are vital for interactions with conspecifics later in life, i.e., aggression, sexual, and social interactions; (C) 1999 John Wiley & Sons, Inc

Occupational burden of disease in the Netherlands

Ongunstige arbeidsomstandigheden veroorzaken 2 tot 4% van de totale ziektelast in Nederland. Het begrip ziektelast is een maatstaf om de gevolgen van ziekte uit te drukken. Het combineert gezondheidsverlies door verminderde kwaliteit van leven en door vroegtijdig overlijden. Hoge werkdruk, blootstelling aan schadelijke stoffen (inclusief passief roken) en beeldschermwerk zijn de ongunstigste arbeidsomstandigheden. Zij zorgen voor veel ziektelast door burn-out, de chronische luchtwegaandoening COPD, longkanker en klachten van arm, nek en schouder (KANS). In het rapport is de positieve invloed van arbeid op de gezondheid niet meegenomen. Het RIVM laat voor het eerst zien welke arbeidsgerelateerde aandoeningen veel ziektelast in Nederland veroorzaken. Deze gegevens bieden aanknopingspunten voor verder onderzoek en voor maatregelen om de ziektelast door deze aandoeningen te verminderen. Dat is niet alleen goed voor werknemers en werkgevers, maar ook voor de volksgezondheid en de samenleving in haar geheel: health is wealth. In eerdere ziektelastberekeningen van de wereldgezondheidsorganisatie (WHO) is de arbeidsgerelateerde ziektelast in Nederland sterk onderschat. In Nederland veroorzaken niet zozeer de 'klassieke' risico's en aandoeningen, zoals arbeidsongevallen en slechthorendheid door lawaai, de meeste ziektelast. Juist 'nieuwe' aandoeningen, zoals burn-out en KANS, leiden hiertoe, en die zijn niet meegenomen in de WHO-schattingen. Behalve negatieve effecten op de gezondheid hebben ongunstige arbeidsomstandigheden een nadelig effect op de arbeidsproductiviteit, het ziekteverzuim en arbeidsongeschiktheid. In theorie blijkt het mogelijk om deze effecten te berekenen. Het is aan te bevelen om uit te zoeken of dit in de praktijk haalbaar is.Occupational health risks cause 2 to 4% of the total burden of disease in the Netherlands. The concept of burden of disease is a criterion to express the consequences of disease. It combines the time lived with disability and the time lost due to premature mortality. A high workload, exposure to harmful chemicals (including environmental tobacco smoke) and working with a computer are the most unfavourable working conditions. They contribute most to the occupational burden of disease caused by: burn-out, chronic obstructive pulmonary disease, lung cancer and complaints of arm, neck and shoulder (CANS). The health benefits of work were not included in this report. For the first time, the RIVM shows in this study which occupational diseases contribute most to the burden of disease in the Netherlands. The data offer starting points for further research and measures to reduce the burden of disease caused by these complaints. This is good not only for employers and employees but also for public health and society as a whole: health is wealth. The World Health Organization (WHO) underestimated the occupational burden of disease in the Netherlands in its earlier burden of disease assessments. In the Netherlands, most of the burden of disease is not caused by the 'classical' risks and diseases like accidents and hearing impairment caused by noise. Rather 'new' diseases like burn-out and CANS cause considerable loss of health and were not taken into account in the assessments of the WHO. Unfavourable working conditions do not only have negative effects on health, but also have a disadvantageous effect on productivity, absenteeism and incapacity for work. In theory it is possible to estimate these adverse effects. We therefore advise to study whether estimating them is feasible in practice.SZ